Preform and container having thread groove

ABSTRACT

A finish for a plastic container and a preform adapted to be molded into the plastic container. The finish and the preform include an upper portion having a mouth defining an opening into the container. At least one groove is defined around a radial sidewall of the upper portion. The groove slopes gradually downward along the radial sidewall to a terminal end.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/763,203 filed on Jan. 27, 2006. The disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

This disclosure generally relates to plastic containers for retaining acommodity, and in particular a liquid commodity. More specifically, thisdisclosure relates to a plastic preform and resultant container having agroove formed in the molded surface where threads of a given closurewill ride during capping.

BACKGROUND

As a result of environmental and other concerns, plastic containers,more specifically polyester and even more specifically polyethyleneterephthalate (PET) containers are now being used more than ever topackage numerous commodities previously supplied in glass containers.Manufacturers and fillers, as well as consumers, have recognized thatPET containers are lightweight, inexpensive, recyclable andmanufacturable in large quantities.

Blow-molded plastic containers have become commonplace in packagingnumerous commodities. PET is a crystallizable polymer, meaning that itis available in an amorphous form or a semi-crystalline form. Theability of a PET container to maintain its material integrity relates tothe percentage of the PET container in crystalline form, also known asthe “crystallinity” of the PET container. The following equation definesthe percentage of crystallinity as a volume fraction:

${\%\mspace{14mu}{Crystallinity}} = {( \frac{\rho - \rho_{a}}{\rho_{c} - \rho_{a}} ) \times 100}$where ρ is the density of the PET material; ρ_(a) is the density of pureamorphous PET material (1.333 g/cc); and ρ_(c) is the density of purecrystalline material (1.455 g/cc).

Container manufacturers use mechanical processing and thermal processingto increase the PET polymer crystallinity of a container. Mechanicalprocessing involves orienting the amorphous material to achieve strainhardening. This processing commonly involves stretching an injectionmolded PET preform along a longitudinal axis and expanding the PETpreform along a transverse or radial axis to form a PET container. Thecombination promotes what manufacturers define as biaxial orientation ofthe molecular structure in the container. Manufacturers of PETcontainers currently use mechanical processing to produce PET containershaving approximately 20% crystallinity in the container's sidewall.

Thermal processing involves heating the material (either amorphous orsemi-crystalline) to promote crystal growth. On amorphous material,thermal processing of PET material results in a spherulitic morphologythat interferes with the transmission of light. In other words, theresulting crystalline material is opaque, and thus, generallyundesirable. Used after mechanical processing, however, thermalprocessing results in higher crystallinity and excellent clarity forthose portions of the container having biaxial molecular orientation.The thermal processing of an oriented PET container, which is known asheat setting, typically includes blow molding a PET preform against amold heated to a temperature of approximately 250° F.-350° F.(approximately 121° C.-177° C.), and holding the blown container againstthe heated mold for approximately two (2) to five (5) seconds.Manufacturers of PET juice bottles, which must be hot-filled atapproximately 185° F. (85° C.), currently use heat setting to producePET bottles having an overall crystallinity in the range ofapproximately 25%-35%.

Typically, an upper portion of the plastic container defines an opening.This upper portion is commonly referred to as a finish and includes somemeans for engaging a cap or closure to close off the opening. In thetraditional injection-stretch blow molding process, the finish remainssubstantially in its injection molded state while the container body isformed below the finish. The finish may include at least one threadextending radially outwardly around an annular sidewall defining athread profile. In one application, a closure member or cap may define acomplementary thread, or threads, that are adapted to cooperatively matewith the threads of the finish. Generally, clockwise rotation of the capencourages an upper surface of the cap threads to be retained by lowersurfaces of the threads on the finish. In some applications, however,external thread profiles formed on the finish may require anon-desirable large amount of material to manufacture.

SUMMARY

Accordingly, the present disclosure provides a finish for a plasticcontainer including an upper portion having a mouth defining an openinginto the container. At least one groove is defined around a radialsidewall of the upper portion. The groove slopes gradually downwardalong the radial sidewall and away from the opening.

A preform adapted to be molded into a plastic container includes anupper portion having a mouth defining an opening into the container. Thepreform includes at least one groove defined around a radial sidewall ofthe upper portion. The groove slopes gradually downward along the radialsidewall to a terminal end.

A closure member is adapted to selectively mate with a finish on acontainer. The closure member includes a lower portion defining anopening and an upper portion defining a cover. At least one thread isformed on an inner surface of a radial sidewall extending between thelower portion and the upper portion.

Additional benefits and advantages of the present disclosure will becomeapparent to those skilled in the art to which the present disclosurerelates from the subsequent description and the appended claims, takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a finish of a plastic containerconstructed in accordance with the teachings of the present disclosure;

FIG. 2 is a top plan view of the finish of FIG. 1;

FIG. 3 is a side view of the finish of FIG. 1;

FIG. 4 is a sectional view of the finish taken along line 4-4 of FIG. 3;

FIG. 5 is a perspective view of a preform used for construction of anexemplary plastic container having the finish of FIG. 1;

FIG. 6 is a side view of the preform of FIG. 5 shown with an exemplarymolded container in phantom;

FIG. 7 is a sectional view of the preform taken along line 7-7 of FIG.6;

FIG. 8 is a top plan view of the preform of FIG. 5; and

FIG. 9 is a sectional view of a closure member or cap having atamper-evidence band and constructed in accordance with the teachings ofthe present disclosure, the cap shown assembled onto the containerfinish shown in FIG. 1.

DETAILED DESCRIPTION

The following description is merely exemplary in nature, and is in noway intended to limit the disclosure or its application or uses.

This disclosure provides for a container finish having a significantlyreduced weight, while enhancing the interface between a closure memberor cap and the container, and meeting filling line temperature and speeddemands. Significant weight reductions are achieved through theelimination of material from the container wall of a standard threadprofile as well as the elimination of material in other areas of thefinish, which represent areas where plastic can be removed withoutnegatively affecting the sealability function of the closure member orcap and the container.

Additionally, a by-product of the disclosed container finish is animprovement to closure function. In this regard, the disclosed finishmay be less damaging to frangible connectors incorporated intamper-evidence closures, reducing the potential for prematureclosure/tamper-evidence band separation during application. Thesmoother, more cylindrical finish disclosed provides an opportunity tokeep an applied closure member or cap more concentric with the finish,reducing the potential for uneven loading on the frangible connectorswhich secure the tamper-evidence band to the body of the closure memberor cap. Such stability improves tamper-evidence band separation.

Traditionally, the distance between the top seal surface of a containerand the start of the container's threads varies slightly during normalproduction. As this distance varies, it affects the rotational positionof an applied closure, and thus the relative location of thetamper-evidence band retention features to the mating features on thefinish. The disclosed container finish eliminates the above-mentioneddistance and variability, and thereby contributes to improvedtamper-evidence band closure performance.

With initial reference to FIGS. 1-4, a finish of a plastic, e.g.polyethylene terephthalate (PET), hot-fillable container is shown andgenerally identified at reference numeral 10. A closure member or cap 12(FIG. 9, described in detail later) may be used to selectively mate withthe finish 10 in a closed or assembled position. The finish 10 of thepresent teachings includes a top 14 defining a mouth or opening 16, anannular sidewall 18 and a support ring 24. The opening 16 allows theplastic container to receive a commodity. The annular sidewall 18generally defines a groove region 28. The groove region 28 provides ameans for attachment of the closure member or cap 12. The groove region28 is formed by a pair of grooves 30 generally defining a helicalpattern. Each groove 30 initiates at a groove entrance 32 and sweepsgradually downward about 180 degrees to about 220 degrees around theannular sidewall 18 of the finish 10 to a terminal end 31. Accordingly,the terminal end 31 prevents over torquing of the closure member or cap12, which could compromise the seal integrity of the closure member orcap 12 of the container. The terminal end 31 also aids in orienting theclosure member or cap 12 in relation to the container.

The groove entrance 32 is generally defined at an intersection betweenan inward sweeping radial lip 36 and an outward sweeping radial lip 38.As best illustrated in FIG. 2, the inward sweeping radial lip 36 definesan arcuate path having a decreasing radius R_(I) that decreases in theclockwise direction. The outward sweeping radial lip 38 defines anarcuate path having an increasing radius R_(O) that increases in theclockwise direction. (It will be appreciated that the radius R_(I) ismeasured from the center of the opening 16 to the lip 36, and the radiusR_(O) is measured from the center of the opening 16 to the lip 38.) Aramp 40 (FIG. 1) is defined at the groove entrance 32 and leads into therespective grooves 30. In another example, the top 14 may define aconstant outer radius without incorporating the inward and outwardsweeping radial lips 36 and 38, respectively. It is appreciated that asingle groove, or two or more grooves may be provided on the annularsidewall 18. Lands 42 define surfaces formed between the grooves 30 onthe annular sidewall 18. A radial channel 46 is formed between theannular sidewall 18 and the support ring 24. As will be described ingreater detail later, the radial channel 46 may serve as a means forcapturing a break-away, tamper-evidence (TE) band 47 attached to theclosure member or cap 12. It is appreciated that the radial channel 46may also include notches, ratchets or similar geometry for dislodgingthe break-away, TE band 47 of the closure member or cap 12 during theopening of the container. In another example, the grooves 30 can extendall the way into the radial channel 46 effectively eliminating anyterminal end of the grooves 30 (i.e. terminal end 31 discussed above).

The pair of grooves 30 of the finish 10 each define a debossed (grooved)threaded profile around the annular sidewall 18. When compared totraditional injection molded finishes having an embossed (raised)threaded profile, the finish 10 of the present disclosure may representa material savings of about 15% to about 20% of the overall containerweight and more specifically about 50%, in weight, of traditionalinjection molded finishes. The present disclosure is particularly usefulin hot-fill applications where thicker, heavier finishes have beenrequired to withstand the heat generated from hot-fill processes therebyallowing for traditional opening diameters and finish wall thicknessesto be maintained while significantly light weighting the container.Thus, the disclosed finish 10 is capable of withstanding the rigorsassociated with hot-fill processes, resulting in the same or lessdistortion as is found in traditional container designs having thicker,heavier finishes.

In another advantage over traditional threaded finish containers, afinish 10 having grooves 30 is more comfortable for a user's mouth toengage and therefore drink from. In this way, a user's mouth can restmore comfortably on a finish free of projecting threads. Furthermore, itis easier for a user to form a seal between their mouth and the finish10 having grooves 30 as compared to a finish having projecting threads.

A plastic container may be designed to retain a commodity during athermal process, typically a hot-fill process. For hot-fill bottlingapplications, bottlers generally fill the container with a liquid orproduct at an elevated temperature between approximately 155° F. to 205°F. (approximately 68° C. to 96° C.) and seal the container at the finish10 with the closure member or cap 12 before cooling. In addition, theplastic container may be suitable for other high-temperaturepasteurization or retort filling processes or other thermal processes aswell.

Turning now to FIGS. 3 and 4, exemplary dimensions for the finish 10will be described. It is appreciated that other dimensions may be used.A diameter D1 of the finish 10 taken at the lands 42 of the annularsidewall 18 may be 39.24 mm (1.55 inches). A diameter D2 of the finish10 taken at the grooves 30 of the annular sidewall 18 may be 36.86 mm(1.45 inches). Accordingly, the diameter D2 may be at least 1 mm (0.04inch) less than the diameter D1. A diameter D3 of the finish 10 taken atthe radial channel 46 may be 37.47 mm (1.48 inches). Similarly, thediameter D3 may be at least 1 mm (0.04 inch) less than the diameter D1.As such, the diameter D2 and the diameter D3 may be less than thediameter D1. A diameter D4 of the finish 10 taken at the support ring 24may be 44.48 mm (1.75 inches). As a result of the reduction in the capdiameter, the diameter D4 is similarly reduced. A height H1 taken fromthe top 14 to the beginning of the radial channel 46 may be 8.51 mm(0.34 inch). A height H2 of the support ring 24 may be 1.15 mm (0.05inch). A height H3 of the radial channel 46 may be 3.18 mm (0.13 inch).A height H4 taken from the top 14 to the first groove 30 at thecompletion of the ramp 40 may be 1 mm (0.04 inch). A height H5, or aheight of the groove 30, may be 2.39 mm (0.09 inch). A height H8, or aheight of the land 42, may be 1.52 mm (0.06 inch). A seal width W may be0.82 mm (0.03 inch). In this regard, the seal width W may not be greaterthan about 50% to about 60% of a wall thickness T2 taken from land 42 tothe inner diameter of the opening 16.

With continued reference to FIG. 4, various radii will now be listedwith exemplary dimensions. R1, R2, R4 and R5 may be 0.25 mm (0.01 inch).R3 may be 0.76 mm (0.03 inch). R6, R8 and R9 may be 0.51 mm (0.02 inch).R7 may be 1.02 mm (0.04 inch). As such, a minimum dimension for R1, R2,R4, R5, R6, R7 and R9 may be 0.1 mm (0.004 inch). Again, it isappreciated that other dimensions may be used. However, theabove-described dimensions provide the closure member or cap 12 withgood spin capabilities when engaging the grooves 30.

Turning now to FIGS. 5-8, a preform 50 used to mold an exemplarycontainer having the finish 10 will be described. The plastic containerof the present teachings is a blow molded, biaxially oriented containerwith a unitary construction from a single or multi-layer material. Awell-known stretch-molding, heat-setting process for making hot-fillableplastic containers generally involves the manufacture of the preform 50through injection molding of a polyester material, such as polyethyleneterephthalate (PET), having a shape well known to those skilled in theart similar to a test-tube with a generally cylindrical cross sectionand a length typically approximately fifty percent (50%) that of theresultant container height. A machine (not illustrated) places thepreform 50 heated to a temperature between approximately 190° F. to 250°F. (approximately 88° C. to 121° C.) into a mold cavity (notillustrated) having a shape similar to the resultant plastic container.

The mold cavity (not illustrated) may be heated to a temperature betweenapproximately 250° F. to 350° F. (approximately 121° C. to 177° C.). Astretch rod apparatus (not illustrated) stretches or extends the heatedpreform 50 within the mold cavity to a length approximately that of theresultant container thereby molecularly orienting the polyester materialin an axial direction generally corresponding with a centrallongitudinal axis of the resultant container. While the stretch rodextends the preform 50, air having a pressure between 300 PSI to 600 PSI(2.07 MPa to 4.14 MPa) assists in extending the preform 50 in the axialdirection and in expanding the preform 50 in a circumferential or hoopdirection thereby substantially conforming the polyester material to theshape of the mold cavity and further molecularly orienting the polyestermaterial in a direction generally perpendicular to the axial direction,thus establishing the biaxial molecular orientation of the polyestermaterial in most of the container. Typically, material within the finish10 and a sub-portion of the base are not substantially molecularlyoriented. The pressurized air holds the mostly biaxial molecularlyoriented polyester material against the mold cavity for a period ofapproximately two (2) to five (5) seconds before removal of thecontainer from the mold cavity.

Alternatively, other manufacturing methods using other conventionalmaterials including, for example, polypropylene, high densitypolyethylene, polyethylene naphthalate (PEN), a PET/PEN blend orcopolymer, and various multilayer structures may be suitable for themanufacture of plastic containers. Those having ordinary skill in theart will readily know and understand plastic container manufacturingmethod alternatives.

The preform 50 may be defined in terms of complementary features of afinished container. For exemplary purposes, a formed container 56 isshown in phantom in FIG. 6. As such, the container 56 may include ashoulder region 60. The shoulder region 60 merges into and provides atransition between the finish 10 and a sidewall portion 62. The sidewallportion 62 extends downward from the shoulder region 60 to a base 64.The base 64 functions to close off the bottom portion of the plasticcontainer 56 and, together with the finish 10, the shoulder region 60,and the sidewall portion 62, to retain the commodity. The specificconstruction of the shoulder region 60, the sidewall portion 62 and thebase 64 are merely exemplary and may vary according to particularapplications. The support ring 24 may be used to carry or orient thepreform 50 through and at various stages of manufacture. For example,the preform 50 may be carried by the support ring 24, the support ring24 may be used to aid in positioning the preform 50 in the mold, or anend consumer may use the support ring 24 to carry the plastic container56 once manufactured.

With specific reference now to FIGS. 7 and 8, exemplary dimensions forthe preform 50 will be described. It is appreciated that the finish 10of the preform 50 is equivalent to the finish 10 as described in FIGS.1-4. As such, similar reference numerals will be used to designate likecomponents. An inner diameter D5 of the opening 16 may be 34.08 mm (1.34inches). A height H6 taken from the top 14 of the finish 10 to thebottom of the support ring 24 may be 13.49 mm (0.53 inch). A height H7taken from the top 14 of the finish 10 to an onset 6566 of the preform50 shoulder region may be 14.30 mm (0.56 inch). A wall thickness T1taken at the preform 50 shoulder region may be 3.62 mm (0.14 inch). Thewall thickness T2 taken from land 42 to the inner diameter of theopening 16 may be 2.09 mm (0.08 inch). An angle A1 taken from alongitudinal centerline 67 to an inner wall surface 68 may be 27degrees. An angle A2 taken from the longitudinal centerline 67 to anouter wall surface 69 may be 20 degrees.

With reference to FIG. 9, the closure member or cap 12 is shown engagedto the finish 10 in a closed or assembled position. In the assembledposition, the closure member or cap 12 engages the finish 10 topreferably provide a hermetical seal to the plastic container 56. Theclosure member or cap 12 is preferably of a plastic or metal materialsuitable for subsequent thermal processing, including high temperaturepasteurization and retort. According to the present teachings, theclosure member or cap 12 may define raised, outwardly extending threads70 for rotatably engaging the grooves 30 of the finish 10. In theexemplary finish 10, a two lead configuration is shown. As such, a pairof threads 70 defined on the closure member or cap 12 is adapted to bereceived by the complementary pair of grooves 30. While two threads 70are shown in the sectional view of FIG. 9, it is appreciated that one ormore than two threads may be provided. To initiate gripping of thethreads 70 within the respective grooves 30, the closure member or cap12 may be placed on the top 14 and rotated until both leads of threads70 are accepted at the groove entrance 32. The ramp 40 (FIG. 1)progressively directs the respective threads 70 within the grooves 30 asthe closure member or cap 12 is rotated in a clockwise direction. Asexplained above, each of the grooves 30 are defined around approximately180 degrees to approximately 220 degrees of the annular sidewall 18. Torotate the closure member or cap 12 into a sealed position with thefinish 10, the closure member or cap 12 may not need to rotate theentire 180 to 220 degrees. In one example, the threads 70 of the closuremember or cap 12 may rotate approximately 160 degrees to approximately200 degrees around the grooves 30 to attain a sealed position. In otherwords, each of the embossed (raised) threads 70 of the closure member orcap 12 may be lesser in length than each of the respective grooves 30 ofthe finish 10. Additionally, the threads 70 of the closure member or cap12 may be longer than or the same in length as each of the respectivegrooves 30 of the finish 10 in order to orient the closure member or cap12 in relation to the container 56. The finish 10, having debossed(inward) grooves 30 of the current disclosure, enables use of a closuremember or cap 12 being shorter in height and smaller in diameter thancaps currently used with traditional finishes of the same diameterhaving embossed (raised) threads. In one example, an outer diameter ofthe closure member or cap 12 can be reduced to about 41 mm (1.61 inches)as compared to a 43 mm (1.69 inches) outer diameter required for anequivalent conventional cap having grooves. Furthermore, as illustratedin FIG. 9, the outer diameter of the closure member or cap 12 can besubstantially equivalent to an outer diameter defined at the supportring 24. This represents a significant weight savings, as less materialis required for the closure member or cap 12. Accordingly, the finish 10provides the container 56 with the ability to retain the closure memberor cap 12, and withstand the associated application torque while alsoproviding easy removal of the closure member or cap 12.

The closure member or cap 12 is shown with the TE band 47. The closuremember or cap 12 can generally include a cover 80 at an upper end. TheTE band 47 is further defined by a band body 82 and a flap 84 extendingtherefrom. The flap 84 extends generally inboard of the band body 82.The TE band 47 of the closure member or cap 12 is designed to ride overthe annular sidewall 18 of the finish 10 in a forward (downward)direction when the closure member or cap 12 is initially applied to thecontainer 56. When the closure member or cap 12 is initially unscrewed(moved upward), the flap 84 engages the annular sidewall 18 andtherefore breaks away the TE band 47 from the closure member or cap 12.The prevention of the TE band 47 moving back up on the finish 10 whenthe closure member or cap 12 is removed thus creates the necessaryengagement interface and force that effectively removes the TE band 47from the closure member or cap 12, leaving it on the container finish10.

While the above description constitutes the present disclosure, it willbe appreciated that the disclosure is susceptible to modification,variation and change without departing from the proper scope and fairmeaning of the accompanying claims.

1. A plastic container having an upper portion, a body portion extendingfrom said upper portion to a base, said base closing off an end of saidcontainer; said upper portion, said body portion and said basecooperating to define a receptacle chamber within said container intowhich product can be filled, said plastic container comprising: a mouthformed in said upper portion defining an opening into the container; anda radial sidewall of said upper portion defined in part by at least onegroove formed therein, said at least one groove sloping graduallydownward along said radial sidewall and away from said opening, whereineach of said at least one groove initiates at a groove entrance definedat an intersection between an inward sweeping radial lip and an outwardsweeping radial lip.
 2. The container of claim 1 wherein said upperportion further comprises: a radial channel formed adjacent to a lowerportion of said radial sidewall.
 3. The container of claim 2 whereinsaid radial sidewall includes a land adjacent said at least one grooveon an outer diameter thereof, wherein said radial sidewall defines awall thickness measured substantially perpendicular to an axis of saidopening from said land to an innermost surface of an inner diameterthereof, wherein said radial sidewall also defines a seal width measuredsubstantially perpendicular to said axis of said opening from said landto an innermost surface of said at least one groove, and wherein saidseal width of each of said at least one groove is not greater than about50% to about 60% of said wall thickness.
 4. The container of claim 1wherein each of said at least one groove slopes gradually downward about180 degrees to about 220 degrees around said radial sidewall.
 5. Thecontainer of claim 1 wherein said inward sweeping radial lip defines anarcuate path having a decreasing radius in a clockwise direction, saiddecreasing radius measured from a center of said opening to said inwardsweeping radial lip.
 6. The container of claim 1 wherein said outwardsweeping radial lip defines an arcuate path having an increasing radiusin a clockwise direction, said increasing radius measured from a centerof said opening to said outward sweeping radial lip.
 7. A plasticcontainer assembly comprising: a plastic container comprising: a finishhaving a first radial sidewall and formed at an opening into saidcontainer; and at least one groove formed in said first radial sidewall,said at least one groove initiating at a groove entrance defined at anintersection between an inward sweeping radial lip and an outwardsweeping radial lip, said at least one groove sloping gradually awayfrom said opening; and a closure member adapted to selectively mate withsaid first radial sidewall of said container, said closure membercomprising: a lower portion defining a closure opening; an upper portiondefining a cover; and a second radial sidewall extending between saidlower portion and said upper portion, said second radial sidewall havingan inner surface defined in part by at least one thread formed thereon,said at least one thread adapted to cooperatively engage said at leastone groove in an assembled position.
 8. The plastic container assemblyof claim 7 wherein said second radial sidewall further includes atamper-evidence band.
 9. The plastic container assembly of claim 8wherein each of said at least one groove slopes gradually downward about180 degrees to about 220 degrees around said first radial sidewall. 10.The plastic container assembly of claim 7 wherein each of said at leastone thread initiates at a thread entrance and slopes gradually towardsaid cover about 160 degrees to about 200 degrees around said secondradial sidewall.
 11. The plastic container assembly claim 7 wherein saidfirst radial sidewall includes a land adjacent said at least one grooveon an outer diameter thereof, wherein said first radial sidewall definesa wall thickness measured substantially perpendicular to an axis of saidopening from said land to an innermost surface of an inner diameterthereof, wherein said first radial sidewall also defines a seal widthmeasured substantially perpendicular to said axis of said opening fromsaid land to an innermost surface of said at least one groove, andwherein said seal width of each of said at least one groove is notgreater than about 50% to about 60% of said wall thickness.
 12. Theplastic container assembly of claim 7 wherein said closure member isformed of one of a plastic and metal material suitable for thermalprocessing.
 13. A preform adapted to be molded into a plastic container,said preform comprising: an upper portion having a mouth correspondingto an opening into the container; and a radial sidewall of said upperportion defined in part by at least one groove formed therein, said atleast one groove sloping gradually downward along said radial sidewalland away from said opening, wherein each of said at least one grooveinitiates at a groove entrance defined at an intersection between aninward sweeping radial lip and an outward sweeping radial lip.
 14. Thepreform of claim 13 wherein said radial sidewall includes a landadjacent said at least one groove on an outer diameter thereof, whereinsaid radial sidewall defines a wall thickness measured substantiallyperpendicular to an axis of said opening from said land to an innermostsurface of an inner diameter thereof, wherein said radial sidewall alsodefines a seal width measured substantially perpendicular to said axisof said opening from said land to an innermost surface of said at leastone groove, and wherein said seal width of each of said at least onegroove is not greater than about 50% to about 60% of said wallthickness.
 15. The preform of claim 13 wherein each of said at least onegroove slopes gradually downward about 180 degrees to about 220 degreesaround said radial sidewall.
 16. The preform of claim 13 wherein saidinward sweeping radial lip defines an arcuate path having a decreasingradius in a clockwise direction, said decreasing radius measured from acenter of said opening to said inward sweeping radial lip.
 17. Thepreform of claim 13 wherein said outward sweeping radial lip defines anarcuate path having an increasing radius in a clockwise direction, saidincreasing radius measured from a center of said opening to said outwardsweeping radial lip.
 18. The preform of claim 13 wherein a firstdistance measured between an inner wall surface and an outer wallsurface is greater than a second distance measured between an innerdiameter of said opening and an outer diameter of each of said at leastone groove.
 19. The preform of claim 13 wherein a first angle measuredbetween a central longitudinal axis and an inner wall surface is greaterthan a second angle measured between said central longitudinal axis andan outer wall surface.